1. Field of the Invention
The invention is related generally to the field of interpretation of measurements made by well logging instruments for the purpose of determining the properties of earth formations. More specifically, the invention provides techniques for determination of formation dip and azimuth angles using induction measurements.
2. Description of the Related Art
Electromagnetic induction and wave propagation logging tools are commonly used for determination of electrical properties of formations surrounding a borehole. These logging tools give measurements of apparent resistivity (or conductivity) of the formation that, when properly interpreted, are diagnostic of the petrophysical properties of the formation and the fluids therein.
In thinly laminated sand-shale sequences or shaly-sand formations, the formation electrical anisotropy becomes important in determining the hydrocarbon saturation from the resistivity measurements. Due to the complexity of the formation, particularly the variations in the relative dip angle between the borehole axis and the formation dipping, determining the formation electrical anisotropy can be complicated. The deviation of the well and the rotation of the tool make determinations of anisotropy and other quantities more difficult.
There is a need for advanced methods for providing real-time determinations of the relative rotation of a measuring tool and formation dip angles, which provides users with information for further determining formation anisotropy. Preferably, the method should consistently provide accurate and reliable data and be computationally efficient.